Field of the Invention
The present invention relates to a piezoelectric material, and in particular, to a lead-free piezoelectric material. The present invention also relates to a piezoelectric element, a multilayered piezoelectric element, a liquid ejection head, a liquid ejection apparatus, an ultrasonic motor, an optical apparatus, a vibration apparatus, a dust removing device, an image pickup device, and an electronic apparatus, all of which use the piezoelectric material.
Description of the Related Art
Typical piezoelectric materials are ABO3 perovskite-type metal oxides such as lead zirconate titanate (hereinafter referred to as “PZT”). However, PZT contains lead in the A-site of the perovskite skeleton. Therefore, the effect of the lead component on the environment has been regarded as a problem. In order to address this problem, piezoelectric materials and piezoelectric elements that include lead-free perovskite-type metal oxides have been proposed.
Examples of the piezoelectric materials that contain a lead-free perovskite-type oxide include barium titanate (BaTiO3) and derivatives thereof. Japanese Patent No. 5217997 discloses a piezoelectric material and a piezoelectric element in which temperature-dependent stability of piezoelectric properties at around room temperature and a mechanical quality factor are improved by substituting some of the A-sites of barium titanate with calcium (Ca) and some of the B-sites of barium titanate with manganese (Mn), iron (Fe), or copper (Cu). The improvement in the mechanical quality factor is effective to reduce heat generation during driving of a piezoelectric element and to reduce the power consumption of the piezoelectric element. However, there may be a problem in that the piezoelectric properties of the piezoelectric material disclosed in Japanese Patent No. 5217997 are lower than those of unsubstituted barium titanate in a temperature range (−30° C. to 50° C.) in which a device is driven.
As other examples, Japanese Patent Laid-Open No. 2009-215111 and the “Journal of Applied Physics” 2011, Vol. 109, 054110-1 to 054110-6 disclose piezoelectric materials in which piezoelectric properties are improved by substituting some of the A-sites of barium titanate with calcium (Ca) and substituting some of the B-sites thereof with zirconium (Zr). These piezoelectric materials have a low Curie temperature of 80° C. or lower and cause depolarization in a high-temperature environment, for example, in a car in the summer, resulting in a problem of a decrease in piezoelectric properties thereof. In general, piezoelectric properties of a piezoelectric element that has been subjected to a polarization treatment are significantly decreased by depolarization at a temperature 10° C. to 20° C. lower than the Curie temperature. In addition, the piezoelectric material disclosed in Japanese Patent Laid-Open No. 2009-215111 has a small mechanical quality factor in the device-driving temperature range (−30° C. to 50° C.)
That is, the piezoelectric materials in the related art have a problem in that, in the device-driving temperature range (−30° C. to 50° C.), a piezoelectric constant is small in a high-temperature range and a mechanical quality factor is small in a low-temperature range.
The present invention provides a lead-free piezoelectric material having a good piezoelectric constant and a good mechanical quality factor in a device-driving temperature range. The present invention further provides a piezoelectric element, a multilayered piezoelectric element, a liquid ejection head, a liquid ejection apparatus, an ultrasonic motor, an optical apparatus, a vibration apparatus, a dust removing device, an image pickup device, and an electronic apparatus, all of which use the piezoelectric material.